fix many internal links

Fixed a number of internal links that need to
go to the GitHub site.

Ran `make www` to perform the above.

2012/tromp/index.html

@@ -715,7 +715,7 @@ many warnings;</p>
 and detract from its single minded focus on conciseness.</p>
 <p>It implicitly declares functions <code>read(2)</code>, <code>write(2)</code>, <code>exit(3)</code> and
 <code>calloc(3)</code>, the latter two incompatibly. 32 bit and 64 bit executables are
-separate <a href="Makefile">Makefile</a> targets, involving a change from <code>int</code> to <code>long</code>
+separate <a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2012/tromp/Makefile">Makefile</a> targets, involving a change from <code>int</code> to <code>long</code>
 and from a hardcoded sizeof of 4 to 8.</p>
 <p>The program has been tested to work correctly on Linux/Solaris/MacOSX both in 32
 and 64 bits.</p>